This invention relates to an infrared and ultraviolet radiation absorbing glass and a method of producing the glass. The glass has a greenish color and sufficiently high transmittance for visible light and is particularly suitable for use in building and vehicle windows.
For windows of buildings, automobiles and other vehicles there is an increasing demand for sheet glass that is sufficiently transparent to visible light and absorptive of not only infrared rays but also ultraviolet rays.
It is known to render a soda-lime-silica glass absorptive of infrared and ultraviolet rays by incorporating iron in the glass. Ferrous iron expressed as FeO provides the glass with the absorption of infrared radiation, whereas ferric iron expressed as Fe.sub.2 O.sub.3 provides the glass with the absorption of ultraviolet radiation. In practice Fe.sub.2 O.sub.3 is used as the source of the entire iron, and an adequate portion of Fe.sub.2 O.sub.3 is reduced to FeO during the glassmaking process.
Also it is known to incorporate CeO.sub.2 and/or TiO.sub.2 in a soda-lime-silica glass for the absorption of ultraviolet radiation.
From an industrial point of view, it is desired that an infrared and ultraviolet absorbing glass in the form of sheet glass can be produced without significantly changing the conditions of conventional glass melting and refining operations. Also it is desired that an infrared and ultraviolet absorbing glass sheet can easily be toughened by a conventional tempering method. Besides, an infrared and ultraviolet absorbing glass sheet is desired to have a pleasing tint such as a greenish tint or a bluish tint.
U.S. Pat. No. 4,792,536 shows an infrared and ultraviolet absorbing glass and a method of producing the same. Basically the glass is a soda-lime-silica glass. In the glass, the content of total iron expressed as Fe.sub.2 O.sub.3 is up to 1 wt %, and preferably 0.45-0.65 wt %, and at least 35% of the total iron is in the ferrous state as FeO. Besides, the glass contains up to 1.5 wt % of CeO.sub.2 and/or TiO.sub.2. An important feature of the glass of this patent is that the content of SO.sub.3 is less than 0.02 wt %.
From an industrial point of view, the proposal of U.S. Pat. No. 4,792,536 is not favorable because the proposed glass cannot be produced by the conventional glass-melting operations. As is disclosed in the patent specification, due to the very low content of sulfur, it is necessary to employ a complicated two-stage melting and refining operations by using a special stirring means.
U.S. Pat. No. 5,077,133 shows a green-colored, infrared energy and ultraviolet radiation absorbing soda-lime-silica glass containing 0.51-0.96 wt % of Fe.sub.2 O.sub.3, 0.15-0.33 wt % of FeO and 0.2-1.4 wt % of CeO.sub.2. In this glass, the total amount of iron is from 0.7 wt % to about 1.25 wt %, expressed as Fe.sub.2 O.sub.3, and the degree of reduction from ferric to ferrous iron is from 23% to 29%. The degree of reduction of this glass is relatively low, and it is necessary to add a relatively large amount of total iron to the glass batch composition. Furthermore, it is not easy to desirably toughen this glass by a conventional tempering method.
WO 91/11402 shows a green-colored, infrared and ultraviolet radiation absorbing soda-lime-silica glass containing 0.75-1.2 wt % of total iron expressed as Fe.sub.2 O.sub.3, 0.2-1.4 wt % of CeO.sub.2, and a small amount of carbon (from about 0.15 to about 0.7 pounds per 1,000 pounds of glass). This glass also has a relatively low degree of reduction from ferric to ferrous iron, ranging from about 22% to 29%, and it is necessary to add a relatively large amount of total iron and a small amount of carbon to the glass batch composition. Furthermore, it is not easy to desirably toughen this glass by a conventional tempering method.